Subject: CVE-2024-26633: ip6_tunnel: fix NEXTHDR_FRAGMENT handling in ip6_tnl_parse_tlv_enc_lim()

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

ip6_tunnel: fix NEXTHDR_FRAGMENT handling in ip6_tnl_parse_tlv_enc_lim()

syzbot pointed out [1] that NEXTHDR_FRAGMENT handling is broken.

Reading frag_off can only be done if we pulled enough bytes
to skb->head. Currently we might access garbage.

[1]
BUG: KMSAN: uninit-value in ip6_tnl_parse_tlv_enc_lim+0x94f/0xbb0
ip6_tnl_parse_tlv_enc_lim+0x94f/0xbb0
ipxip6_tnl_xmit net/ipv6/ip6_tunnel.c:1326 [inline]
ip6_tnl_start_xmit+0xab2/0x1a70 net/ipv6/ip6_tunnel.c:1432
__netdev_start_xmit include/linux/netdevice.h:4940 [inline]
netdev_start_xmit include/linux/netdevice.h:4954 [inline]
xmit_one net/core/dev.c:3548 [inline]
dev_hard_start_xmit+0x247/0xa10 net/core/dev.c:3564
__dev_queue_xmit+0x33b8/0x5130 net/core/dev.c:4349
dev_queue_xmit include/linux/netdevice.h:3134 [inline]
neigh_connected_output+0x569/0x660 net/core/neighbour.c:1592
neigh_output include/net/neighbour.h:542 [inline]
ip6_finish_output2+0x23a9/0x2b30 net/ipv6/ip6_output.c:137
ip6_finish_output+0x855/0x12b0 net/ipv6/ip6_output.c:222
NF_HOOK_COND include/linux/netfilter.h:303 [inline]
ip6_output+0x323/0x610 net/ipv6/ip6_output.c:243
dst_output include/net/dst.h:451 [inline]
ip6_local_out+0xe9/0x140 net/ipv6/output_core.c:155
ip6_send_skb net/ipv6/ip6_output.c:1952 [inline]
ip6_push_pending_frames+0x1f9/0x560 net/ipv6/ip6_output.c:1972
rawv6_push_pending_frames+0xbe8/0xdf0 net/ipv6/raw.c:582
rawv6_sendmsg+0x2b66/0x2e70 net/ipv6/raw.c:920
inet_sendmsg+0x105/0x190 net/ipv4/af_inet.c:847
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
__sys_sendmsg net/socket.c:2667 [inline]
__do_sys_sendmsg net/socket.c:2676 [inline]
__se_sys_sendmsg net/socket.c:2674 [inline]
__x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was created at:
slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768
slab_alloc_node mm/slub.c:3478 [inline]
__kmem_cache_alloc_node+0x5c9/0x970 mm/slub.c:3517
__do_kmalloc_node mm/slab_common.c:1006 [inline]
__kmalloc_node_track_caller+0x118/0x3c0 mm/slab_common.c:1027
kmalloc_reserve+0x249/0x4a0 net/core/skbuff.c:582
pskb_expand_head+0x226/0x1a00 net/core/skbuff.c:2098
__pskb_pull_tail+0x13b/0x2310 net/core/skbuff.c:2655
pskb_may_pull_reason include/linux/skbuff.h:2673 [inline]
pskb_may_pull include/linux/skbuff.h:2681 [inline]
ip6_tnl_parse_tlv_enc_lim+0x901/0xbb0 net/ipv6/ip6_tunnel.c:408
ipxip6_tnl_xmit net/ipv6/ip6_tunnel.c:1326 [inline]
ip6_tnl_start_xmit+0xab2/0x1a70 net/ipv6/ip6_tunnel.c:1432
__netdev_start_xmit include/linux/netdevice.h:4940 [inline]
netdev_start_xmit include/linux/netdevice.h:4954 [inline]
xmit_one net/core/dev.c:3548 [inline]
dev_hard_start_xmit+0x247/0xa10 net/core/dev.c:3564
__dev_queue_xmit+0x33b8/0x5130 net/core/dev.c:4349
dev_queue_xmit include/linux/netdevice.h:3134 [inline]
neigh_connected_output+0x569/0x660 net/core/neighbour.c:1592
neigh_output include/net/neighbour.h:542 [inline]
ip6_finish_output2+0x23a9/0x2b30 net/ipv6/ip6_output.c:137
ip6_finish_output+0x855/0x12b0 net/ipv6/ip6_output.c:222
NF_HOOK_COND include/linux/netfilter.h:303 [inline]
ip6_output+0x323/0x610 net/ipv6/ip6_output.c:243
dst_output include/net/dst.h:451 [inline]
ip6_local_out+0xe9/0x140 net/ipv6/output_core.c:155
ip6_send_skb net/ipv6/ip6_output.c:1952 [inline]
ip6_push_pending_frames+0x1f9/0x560 net/ipv6/ip6_output.c:1972
rawv6_push_pending_frames+0xbe8/0xdf0 net/ipv6/raw.c:582
rawv6_sendmsg+0x2b66/0x2e70 net/ipv6/raw.c:920
inet_sendmsg+0x105/0x190 net/ipv4/af_inet.c:847
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
__sys_sendmsg net/socket.c:2667 [inline]
__do_sys_sendmsg net/socket.c:2676 [inline]
__se_sys_sendmsg net/socket.c:2674 [inline]
__x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

CPU: 0 PID: 7345 Comm: syz-executor.3 Not tainted 6.7.0-rc8-syzkaller-00024-gac865f00af29 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023

The Linux kernel CVE team has assigned CVE-2024-26633 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 4.10 with commit fbfa743a9d2a and fixed in 4.19.306 with commit 135414f300c5
	Issue introduced in 4.10 with commit fbfa743a9d2a and fixed in 5.4.268 with commit 3f15ba3dc14e
	Issue introduced in 4.10 with commit fbfa743a9d2a and fixed in 5.10.209 with commit da23bd709b46
	Issue introduced in 4.10 with commit fbfa743a9d2a and fixed in 5.15.148 with commit 4329426cf6b8
	Issue introduced in 4.10 with commit fbfa743a9d2a and fixed in 6.1.75 with commit 62a1fedeb14c
	Issue introduced in 4.10 with commit fbfa743a9d2a and fixed in 6.6.14 with commit 687c5d52fe53
	Issue introduced in 4.10 with commit fbfa743a9d2a and fixed in 6.7.2 with commit ba8d904c2742
	Issue introduced in 4.10 with commit fbfa743a9d2a and fixed in 6.8 with commit d375b98e0248
	Issue introduced in 3.2.87 with commit a6f6bb6bc04a
	Issue introduced in 3.10.106 with commit 72bbf335e7aa
	Issue introduced in 3.12.71 with commit decccc92ee0a
	Issue introduced in 3.16.42 with commit d3d9b59ab321
	Issue introduced in 3.18.49 with commit d397f7035d2c
	Issue introduced in 4.4.50 with commit 41e07a7e01d9
	Issue introduced in 4.9.11 with commit a7fe4e5d0633

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-26633
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	net/ipv6/ip6_tunnel.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/135414f300c5db995e2a2f3bf0f455de9d014aee
	https://git.kernel.org/stable/c/3f15ba3dc14e6ee002ea01b4faddc3d49200377c
	https://git.kernel.org/stable/c/da23bd709b46168f7dfc36055801011222b076cd
	https://git.kernel.org/stable/c/4329426cf6b8e22b798db2331c7ef1dd2a9c748d
	https://git.kernel.org/stable/c/62a1fedeb14c7ac0947ef33fadbabd35ed2400a2
	https://git.kernel.org/stable/c/687c5d52fe53e602e76826dbd4d7af412747e183
	https://git.kernel.org/stable/c/ba8d904c274268b18ef3dc11d3ca7b24a96cb087
	https://git.kernel.org/stable/c/d375b98e0248980681e5e56b712026174d617198